Autorelight 737 during take off

[Boss du Manche]

Hi all,

I was wondering if the 737 does autorelight or is trying to during the take off-phase.

I was of the impression that this was not the case, because of safety-issues. Then it might be possible that you get a lot of yaw during the take off. I recall reading somewhere that autorelight does not work with ingnition in CONT during the take off, which is always the case.

Thats why, in my opinion, you have the possibility for example to do an inflight restart.

So please, is the systemlogic such that autorelight is disabled during the take off roll.

[tdracer]

Not sure if the CFM-7 inhibits igniter firing at high power (some FADEC engines do, don't know about the CFM), but when the burner pressure it at takeoff values (~350-400 psi), the igniters can not spark. Burner pressure needs to get down below ~200 psi before the igniters can actually fire (above that the charge simply dissipates through the igniter system components - which is very hard on the component life hence the reason it's sometimes inhibited).


If an engine were to flameout at takeoff power (very, very unlikely BTW), the igniters won't start to spark until the engine has spooled down and burner pressure dropped sufficiently. Once that happens, continuous ignition/auto-relight will do it's thing. If that will relight and restore engine power is a totally different question :rolleyes: